But few have been British. A show unknown in America is never likely to get the £94million budget that it took to bring Mission Impossible 4 to the screen.

So how is The Sweeney, Thames TV’s gritty police drama from 1975-78, about to get an international release? How does a cult British show, best remembered by British men in their 50s, become a fi lm which, as of next month, will be vying for teenage dollars from Salt Lake City to Shanghai?

As the British cast and crew told us, it takes cunning, resourcefulness and the help of Top Gear and Boris Johnson.

Here’s how...

1. FIND $5MILLION: Twentieth Century Fox were set to remake The Sweeney in 2007, but when the financial crisis hit it went into “turnaround”, as they call it when a studio decides not to make a film. This is usually the kiss of death.

That’s when Nick Love, British director of low-budget films like The Football Factory, took up the reins.

“The rights were owned by an Anglo-German firm called Fremantle,” says Love. “When Fox decided not to do the film, Fremantle gave it to me to do on a small budget.” Love sat down with five producers to work out how The Sweeney could be turned into a hit.

“It was a challenge,” says Chris Simon, one of the five. “People were willing to help for a love of The Sweeney. That kept the budget low.” How low? “You could certainly make a film like this for $5million. But not easily...”

2. CAST A COCKNEY LEGEND: The original Sweeney starred the late John Thaw as the Flying Squad’s “thief-taker general”, DI Jack Regan. Only one actor was ever in the frame to play Regan this time: Ray Winstone.

After all, his first appearance on The Sweeney was 35 years ago.

“It was my first ever job,” says Winstone. “I was an extra on an episode called Loving Arms. I was a good-looking geezer back then and God, I’m ugly now.”

3. DON’T CALL IT A REMAKE: “It’s not a remake,” says producer Chris Simon. “A reboot, maybe. We have Regan, Carter and one catchphrase, but apart from that, all we’ve retained from the original is the attitude.”

If you’re wondering, the one catchphrase is: “Get your trousers on, you’re nicked.” Winstone says it to a villain in boxer shorts at the end of a violent car chase.

4. DON’T GO RETRO: Kipper ties, Cortinas and casual sexism: the temptation was to set The Sweeney in the late 70s. But that’s already been done in the TV series Life On Mars. There was no choice but to go in the opposite direction and set the new Sweeney in modern London.

“I wanted it to be sharp and contemporary,” says Love. “Doing it as a 70s movie would restrict you to filming in the tiny bits of London that still look like they did then, and there aren’t many.

“I was born in 1957 and grew up in Plaistow,” says Winstone. “There were bombed-out houses and when you watch the original Sweeney. You can still see them round Hammersmith and Shepherd’s Bush where they filmed it.”

The Sweeney in the new film work out of a glass and steel office with superb views across the City.

The opening scene is a helicopter shot of the Docklands at night. It’s a far cry from smoky pubs and brown Granadas.

5. FIND A RISING STAR: In the first episode of the original, Regan needed a partner who could throw a punch and knew his way around the criminal underworld. He picked DS George Carter, played by former boxer Dennis Waterman. The modern Carter had to be as tough.

“We saw some very successful actors,” says Ray Winstone. “But as soon as I saw Ben I thought: number one, he looks like he could kick down a door, and number two, he can act.”

Ben Drew is more famous as Plan B, the Brit Award-winning hip-hop artist from east London. He’d already released two hit albums and had appeared in the films Adulthood and Harry Brown (the latter opposite Michael Caine). He was also working on his directorial debut, the sink-estate drama Ill Manors. That film, and the accompanying album, which went to No 1 last month, have since massively boosted Drew’s profile. Good news for The Sweeney.

“I nearly pulled out, though,” says Drew. “To be honest, I didn’t want to be a Batman and Robin sidekick.

“Ray persuaded me that if he was a real cop he’d want someone my age as a partner, someone who spoke the language the kids speak. There’s a lot less Cockney on the streets of London now. I guess it’s a Jamaican influence.

“Old boys wouldn’t understand a word that comes out of a kid’s mouth. That’s when I realised we had our own thing and we weren’t trying to be Thaw and Waterman. We just took the name and the basic elements of The Sweeney and reinvented it.”

6. DO YOUR RESEARCH: The cast were in place. But who would the villains be? It was always East End crime gangs in the 70s version. Is that realistic these days? Nick Love asked members of the real Flying Squad.

“They told me crime has changed,” says Love. “Armed robberies still go on – more than we know about, since police protection of information means some stuff doesn’t get reported. From what they said, east Europeans seemed the most realistic choice of baddies.”

7. FILM A GUN FIGHT IN ­TRAFALGAR SQUARE: This is impossible. Go to number 8.

8. FIND A SILENT BULLET: “I always wanted this film to have a gunfight in Trafalgar Square,” says Love. “The authorities said flat-out no, because of the noise. Imagine the 999 calls you’d get from the sound of gunfire. But, by chance, we heard about a blank bullet that fires without sound.”

Armourer on the film, Rob Partridge, says: “I heard from the MoD that they’ve recently started using UTM Silent Blanks, a new type of cartridge which cycles the weapon as real, explosive bullets do, but makes very little noise.

The only sound is that of the mechanical actions of the weapon: click, click, click. They’re used in training by special units whose name we dare not mention.”

9. NOW FILM A GUNFIGHT IN TRAFALGAR SQUARE: There were still an awful lot of people to persuade before the gunfight could be filmed, including Westminster City Council, the Squares Management Team of the GLA, Transport For London and the Metropolitan Police. Then there was the Mayor’s office.

“Boris Johnson is a massive Sweeney fan,” says Love. “He made it happen. It’s amazing how many doors open to you when you say it’s The Sweeney.

“We’d been given four hours on a Sunday morning and I needed to get it done before too large a crowd developed. The law says that you can ask people to stay out of shot but not force them.”

Drew says: “As soon as I heard there was a Trafalgar Square gunfight in The Sweeney, I had to be in it.”

Was it the first time he’d held a gun? “No, but it’s the first time I’ve shot one. The main thing is, you can’t blink when it goes off.”

10. GET TOP GEAR TO FILM YOUR CAR CHASE: Love wanted a car chase, and an incredible one. “The trouble was, Nick’s never done a car chase before,” says Drew.

“So who was he going to ask? Top Gear. That was a touch of genius, I thought.”

Anyone watching the May 7 episode of Top Gear will have seen Jeremy Clarkson and Richard Hammond making a pig’s ear of filming The Sweeney’s car chase, and Nick Love’s furious reaction.

Of course it was a joke. At the same time, Top Gear’s actual cameramen and directors were working on the real scene.

“Jaguar let us have an XFR, which does 0-60mph in less than five seconds,” says Love. “It’s the modern equivalent of the classic getaway, the Mark II Jag, so I gave it to the villain. I wanted the Sweeney to drive something fast but inconspicuous. Ford said I could use their new Focus ST, which does 154mph.”

As Drew says, Top Gear were probably the only people in the country who could get every ounce of that speed down on film and under budget.

“It took six months of planning and right up to the day we didn’t know if it was going to happen or not,” says Simon. “But it was worth it.’